"Tout le monde s'est trompé ce jour-là."

Translation: Everyone made a mistake that day.

[CJ.Dennis]

"se tromper" (reflexive) is to make a mistake.

"tromper" (non-reflexive) is to trick or to deceive.

[Ratchet111653]

Anybody have some tips on ce jour-là? I wouldn't have to build this "that" in this way.

[n6zs]

Without the « -là », "ce jour" could be either "that day" or "this day". This is the standard way the French specify it was "that day".

[biscuitamericain]

''everyone was mistaken on that day'' seems like it should be accepted, to me

[CSA_GW]

Can we say "the whole wide world" for "Tout le monde"?

[CSA_GW]

Must "s'est trompe " = "made ONE mistake"?

I tried " ..made mistakes" and ".. made mistake", both got rejected by duo.

[CSA_GW]

2018-10-05: "...made mistakes " is accepted.